Most precision navigation solutions rely on the Global Positioning System (GPS) to provide accurate positioning information. Despite the advent of several other Global Navigation systems (GNSS), these navigation aids may be unreliable or may not be available. Inertial navigation offers a self-contained navigation solution which provides relative position from a known starting point by integrating platform accelerations and rotation rates provided by an on-board inertial measurement unit (IMU) which consists of three accelerometers and three gyroscopes. An IMU can be used as a stand-alone navigation solution or it can be used to supplement other navigation methods such as a GNSS, for example. Atom interferometry, and more specifically light-pulse atom interferometry (LPAI), may provide precise inertial instruments to form an IMU, or to supplement conventional inertial measurement units and correct their errors to allow for longer periods of inertial-only navigation. The type of light pulses used may drive a variety of atomic state transitions, such as Raman transitions, Bragg transitions to form an atom interferometer, etc., as understood by those skilled in the art.
Conventional LPAI implementations are larger systems which require substantially more volume than is traversed by the atoms due to the associated mechanisms required to prepare, cool, and trap the atomic sample, resulting in the large size of these systems. Additionally, LPAIs typically have dead time between measurements to cool and prepare the atomic samples. This dead time reduces the maximum measurement rate for the LPAI. By the sampling theorem, this limits the bandwidth of an LPAI based IMU to half of the measurement rate. In order to avoid the bandwidth limit imposed by sample preparation, multiple (two or three) time-multiplexed LPAI instruments may be used for each axis, which again increases the size of the overall system, but allows for continuously sampling the inertial signal. Furthermore, in certain applications it is desirable to obtain inertial measurements for multiple axes. In order to create an LPAI based IMU having six Degrees of Freedom (6-DOF, three vector-space spanning (typically orthogonal) acceleration measurements and three rotation rate (or angle) measurements), three separate LPAI instruments (each functioning as an accelerometer and gyroscope) may typically be combined, as is standard practice for constructing conventional IMUs. Thus, creating a 6-DOF LPAI-based IMU may conventionally require twelve to eighteen separate LPAI instruments to provide a continuously sampling inertial instrument. By having multiple LPAI instruments, each having its own atom sample capture mechanisms, there is a substantial volume increase over what is theoretically necessary.